Process Automation

It is no secret that machinery in a plant generates noise. The question has always been “How much?” With increasing frequency, people are observing machinery behavior that was never intended in the original design. This behavior could manifest as a machine that occasionally or constantly resets, machinery that goes off track, or machinery that stops working properly if at all. Much of this behavior can be traced to inter-machine noise.

What creates this noise?

Many machines use Servo drive and Variable Frequency Drives (VFD’s) to control rotating machinery. VFD’s create high frequency noise that radiates out on the input power cable. If a drive cable is close enough to a signal cable the two cables couple, allowing noise from the drive cable to radiate onto the signal cable. The signal can be overwhelmed by the noise and cause false readings. This can then cause the PLC to make incorrect decisions.

Another source of noise is the Silicon Controlled Rectifier (SCR). These devices are often seen in welding and brazing equipment, industrial ovens, and other large applications where systems need to develop or maintain temperatures in the system. As the SCR turns on, the voltage on the input power line momentarily drops because of insufficient power to feed the load. This causes glitches on the power lines within the plant. This glitch may cause a nearby PLC to reset if the glitch duration is long enough.

Finmotor’s solution to noise problems is to install EMC filters on each panel that controls a VFD or SCR. These filters help in two ways by first stopping noise from leaving the machine and also blocking noise from the plant into the machine.

Finmotor is an industry leader in electromagnetic solutions for automated and industrial machinery. The broad range of products includes: EMI/ RFI filters, motor protection, passive and active harmonic filters, line reactors, surge arresters and voltage stabilizers, as well as the development and implementation of customized solutions. Finlab, a Finmotor subsidiary, provides on-site CE Certification, immunity and emission testing to meet all EU requirements.